Paul's Arm

built by Paul Brown

Click on an image to enlarge it
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Target Environment Locomotion Method
Indoors Static
Sensors / Input Devices Actuators / Output Devices
optical sensors
DC Motors
Stepper motors
Control Method Power Source
Tethered AC via tether
CPU Type Operating System
None None
Programming Lanuage Weight
None N/A
Time to build Cost to build
URL for more information

The photos are of an arm and shoulder I built about a year ago. I have since modified the forearm to include a wrist pitch axis, and a roll axis has been added at the elbow joint.

I built the project initially to demonstrate my fabrication skills and to learn more about DC motor control and stepper motor control (the terminal strip at upper left coonects the controller boards to the motors and the controllers are not shown) The controllers are custom built PWM prototypes I designed and built using 556 timers and NPN TO-3 transistors. The motor controllers are "true" pulse width modulation controllers and feature variable frequency and variable pulse width. The sensors are optical at the elbow, and a potentiometer used with multiple voltage comparators to provide multi-step servo resolution feedback for the motor at the shoulder. the H-bridges are industrial quality 5 Amp 4PDT relays with 2 poles/2 throws used as and H bridge and the other 2 used for interlkock and status indication with seperate multi-pole relays used for enabling, relay interlock and status indication.

Power requirements are multi-voltage, requiring 117 VAC, 12 VDC and 5VDC , this is fairly simply accomplished using a surplus 150 watt computer power supply. I am curently is the process of completing the modifications to the wrist pitch axis and building a stepper motor controller and pc interface with auxillary manual switching for all axis.

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